Lung infections in early childhood can result in airways dysfunction later in life. Hypersecretion by airways epithelium of high molecular weight glycoconjugates (HMG), including mucins and proteoglycans, may play an important role in pathophysiology of airways in these individuals as well as children with bronchopulmonary dysplasia, asthma, and cystic fibrosis. The objective of the proposed studies is to elucidate molecular and cellular changes in the secretory functions of tracheal surface epithelium during development and following injury. The developing tracheal surface epithelium of postnatal ferrets will be our experimental model. We propose to identify developmental patterns of secretory cell populations by employing 1) Alcian blue-periodic acid Schiff's staining to identify cells that store glycoconjugates, 2) immunocytochemistry using monoclonal antibodies that specifically recognize mucin and proteoglycan epitopes to identify secretory cell populations and 3) in situ hybridization using mucin peptide cDNA probes to detect mucin producing cells, with or without secretory granules. In addition, we propose to verify the HMG secretory responses of surface epithelium to ionomycin and human neutrophil elastase by immunoassay of HMG released into culture medium and by direct visualization and quantitation of secretory cell degranulation using videomicroscopy. We will also assess the role of growth factors as modulators of secretory cell differentiation and function during development and repair. Following short term injury to ferret tracheal epithelium with sulfur dioxide or nitric acid vapor, alteration of secretory cell populations and function will be assessed. We expect the repair process will, at least in part, recapitulate normal developmental events. However, severe injury may result in departure from orderly reepithelialization, resulting in increased secretory cell numbers and increased secretory rates, perhaps due to augmented sensitivity of cells to secretory agonists. The proposed studies should provide important information concerning HMG secretion in maturing airways and useful insights into the pathogenesis of hypersecretory states resulting from injury.